Viola -  A young woman of aristocratic birth, and the play’s protagonist. Washed up on the shore of Illyria when her ship is wrecked in a storm, Viola decides to make her own way in the world. She disguises herself as a young man, calling herself "Cesario," and becomes a page to Duke Orsino. She ends up falling in love with Orsino—even as Olivia, the woman Orsino is courting, falls in love with Cesario. Thus, Viola finds that her clever disguise has entrapped her: she cannot tell Orsino that she loves him, and she cannot tell Olivia why she, as Cesario, cannot love her. Her poignant plight is the central conflict in the play.

Orsino -  A powerful nobleman in the country of Illyria. Orsino is lovesick for the beautiful Lady Olivia, but becomes more and more fond of his handsome new page boy, Cesario, who is actually a woman—Viola. Orsino is a vehicle through which the play explores the absurdity of love: a supreme egotist, Orsino mopes around complaining how heartsick he is over Olivia, when it is clear that he is chiefly in love with the idea of being in love and enjoys making a spectacle of himself. His attraction to the ostensibly male Cesario injects sexual ambiguity into his character.

Olivia -  A wealthy, beautiful, and noble Illyrian lady, Olivia is courted by Orsino and Sir Andrew Aguecheek, but to each of them she insists that she is in mourning for her brother, who has recently died, and will not marry for seven years. She and Orsino are similar characters in that each seems to enjoy wallowing in his or her own misery. Viola’s arrival in the masculine guise of Cesario enables Olivia to break free of her self-indulgent melancholy. Olivia seems to have no difficulty transferring her affections from one love interest to the next, however, suggesting that her romantic feelings—like most emotions in the play—do not run deep.

Sebastian -  Viola’s lost twin brother. When he arrives in Illyria, traveling with Antonio, his close friend and protector, Sebastian discovers that many people think that they know him. Furthermore, the beautiful Lady Olivia, whom he has never met, wants to marry him. Sebastian is not as well rounded a character as his sister. He seems to exist to take on the role that Viola fills while disguised as Cesario—namely, the mate for Olivia.

Malvolio -  The straitlaced steward—or head servant—in the household of Lady Olivia. Malvolio is very efficient but also very self-righteous, and he has a poor opinion of drinking, singing, and fun. His priggishness and haughty attitude earn him the enmity of Sir Toby, Sir Andrew, and Maria, who play a cruel trick on him, making him believe that Olivia is in love with him. In his fantasies about marrying his mistress, he reveals a powerful ambition to rise above his social class.

Feste -  The clown, or fool, of Olivia’s household, Feste moves between Olivia’s and Orsino’s homes. He earns his living by making pointed jokes, singing old songs, being generally witty, and offering good advice cloaked under a layer of foolishness. In spite of being a professional fool, Feste often seems the wisest character in the play.

Sir Toby -  Olivia’s uncle. Olivia lets Sir Toby Belch live with her, but she does not approve of his rowdy behavior, practical jokes, heavy drinking, late-night carousing, or friends (specifically the idiotic Sir Andrew). Sir Toby also earns the ire of Malvolio. But Sir Toby has an ally, and eventually a mate, in Olivia’s sharp-witted waiting-gentlewoman, Maria. Together they bring about the triumph of chaotic spirit, which Sir Toby embodies, and the ruin of the controlling, self-righteous Malvolio.

Maria -  Olivia’s clever, daring young waiting-gentlewoman. Maria is remarkably similar to her antagonist, Malvolio, who harbors aspirations of rising in the world through marriage. But Maria succeeds where Malvolio fails—perhaps because she is a woman, but, more likely, because she is more in tune than Malvolio with the anarchic, topsy-turvy spirit that animates the play.

Sir Andrew Aguecheek  -  A friend of Sir Toby’s. Sir Andrew Aguecheek attempts to court Olivia, but he doesn’t stand a chance. He thinks that he is witty, brave, young, and good at languages and dancing, but he is actually an idiot.

Antonio -  A man who rescues Sebastian after his shipwreck. Antonio has become very fond of Sebastian, caring for him, accompanying him to Illyria, and furnishing him with money—all because of a love so strong that it seems to be romantic in nature. Antonio’s attraction to Sebastian, however, never bears fruit. Despite the ambiguous and shifting gender roles in the play, Twelfth Night remains a romantic comedy in which the characters are destined for marriage. In such a world, homoerotic attraction cannot be fulfilled.